A.2. Differing features

The table below shows major differences between the standard shell (sh), Bourne Again SHell (bash), Korn shell (ksh) and the C shell (csh).

Shell compatibility

Since the Bourne Again SHell is a superset of sh, all sh commands will also work in bash - but not vice versa. bash has many more features of its own, and, as the table below demonstrates, many features incorporated from other shells.

Since the Turbo C shell is a superset of csh, all csh commands will work in tcsh, but not the other way round.

Table A-2. Differing Shell Features

sh

bash

ksh

csh

Meaning/Action

$

$

$

%

Default user prompt

>|

>|

>!

Force redirection

> file 2>&1

&> file or > file 2>&1

> file 2>&1

>& file

Redirect stdout and stderr to file

{ }

{ }

Expand elements in list

`command`

`command` or $(command)

$(command)

`command`

Substitute output of enclosed command

$HOME

$HOME

$HOME

$home

Home directory

~

~

~

Home directory symbol

~+, ~-, dirs

~+, ~-

=-, =N

Access directory stack

var=value

VAR=value

var=value

set var=value

Variable assignment

export var

export VAR=value

export var=val

setenv varval

Set environment variable

${nnnn}

${nn}

More than 9 arguments can be referenced

"$@"

"$@"

"$@"

All arguments as separate words

$#

$#

$#

$#argv

Number of arguments

$?

$?

$?

$status

Exit status of the most recently executed command

$!

$!

$!

PID of most recently backgrounded process

$-

$-

$-

Current options

. file

source file or . file

. file

source file

Read commands in file

alias x='y'

alias x=y

alias x y

Name x stands for command y

case

case

case

switch or case

Choose alternatives

done

done

done

end

End a loop statement

esac

esac

esac

endsw

End case or switch

exit n

exit n

exit n

exit (expr)

Exit with a status

for/do

for/do

for/do

foreach

Loop through variables

set -f, set -o nullglob|dotglob|nocaseglob|noglob

noglob

Ignore substitution characters for filename generation

hash

hash

alias -t

hashstat

Display hashed commands (tracked aliases)

hash cmds

hash cmds

alias -tcmds

rehash

Remember command locations

hash -r

hash -r

unhash

Forget command locations

history

history

history

List previous commands

ArrowUp+Enter or !!

r

!!

Redo previous command

!str

r str

!str

Redo last command that starts with "str"

!cmd:s/x/y/

r x=ycmd

!cmd:s/x/y/

Replace "x" with "y" in most recent command starting with "cmd", then execute.

if [ $i -eq 5 ]

if [ $i -eq 5 ]

if ((i==5))

if ($i==5)

Sample condition test

fi

fi

fi

endif

End if statement

ulimit

ulimit

ulimit

limit

Set resource limits

pwd

pwd

pwd

dirs

Print working directory

read

read

read

$<

Read from terminal

trap 2

trap 2

trap 2

onintr

Ignore interrupts

unalias

unalias

unalias

Remove aliases

until

until

until

Begin until loop

while/do

while/do

while/do

while

Begin while loop

The Bourne Again SHell has many more features not listed here. This table is just to give you an idea of how this shell incorporates all useful ideas from other shells: there are no blanks in the column for bash. More information on features found only in Bash can be retrieved from the Bash info pages, in the "Bash Features" section.

More information:

You should at least read one manual, being the manual of your shell. The preferred choice would be info bash, bash being the GNU shell and easiest for beginners. Print it out and take it home, study it whenever you have 5 minutes.